Recent data provide strong evidence of the lifesaving potential of a number of drugs for the management of acute myocardial infarction (AMI). However, other commonly-used agents may pose unacceptable risks with few benefits. Although national and local cardiology consensus panels have developed AMI practice guidelines, no information exists from large samples of community hospitals on rates of compliance with these guidelines, nor have guideline dissemination experiments been conducted. Using a RCT design in 45 Minnesota hospitals, we will evaluate the effectiveness and costs of an innovative model for disseminating practice recommendations emanating from state and national AMI guidelines. The intervention combines: (1) recruitment and training of local cardiology opinion leaders to provide group and one-on-one consultations with peers; (2) dissemination of illustrated and concise practice guidelines; and (3) group performance feedback to physicians and nurses. We hypothesize that the intervention will increase physician compliance with locally adopted guidelines aimed at eliminating either under- or over-use of four classes of medications which significantly affect post-AMI survival. The study will answer the following research questions: (1) Among 2400 AMI patients treated in 40 Minnesota hospitals during the baseline year, what proportion of eligible patients receive therapies which improve clinical outcomes and survival (e.g., thrombolytic agents, antiplatelets (e.g., aspirin), IV beta blockers, magnesium sulfate)? (2) What proportion of AMI patients receive potentially,.harmful therapies (e.g., non-indicated use of calcium channel blockers and lidocaine)? (3) Are characteristics of the hospital (e.g., urban versus rural location, size, number of cardiologists/consultants, presence of CCU) associated with variation in rates of compliance with practice guidelines? (4) Are patient characteristics (e.g., age, sex, and insurance status) associated with care not compliant with guidelines? 5) What are the principal knowledge gaps and other barriers to widespread acceptance of guidelines? 6) Based on post-intervention audits of a second cohort of 2400 AMI patients at randomized study and control hospitals, does the experimental intervention increase use of effective therapies (e.g., thrombolytic agents, beta-blockers and aspirin) in eligible patients, and decrease use of non-indicated drugs? (7) What is the cost of the dissemination program and policy significance of the results?